Welcome to the STEREO Learning Center

Image artifacts - Beacon data

STEREO has two separate telemetry streams coming down from each spacecraft, the
space weather beacon telemetry, and the science recorder playback telemetry.
The beacon telemetry contains the most recent data and images, and is
transmitted 24 hours per day. A volunteer network of antenna stations around
the world collect as much as possible of this real-time data stream, and send
it to the STEREO Science Center for processing. However, because the beacon
telemetry rate is very low, the images need to be compressed by large factors,
and are thus of much lower quality than the actual science data.

The science data collected by the STEREO spacecraft are written to the on-board
recorder, which is then read out and transmitted to the ground during daily
telemetry tracks using the NASA Deep Space Network. These data are of much
higher quality than the beacon data, but take several days to reach the STEREO
Science Center website. Thus, the most recent images on the STEREO Science
Center
browse
tool will always be beacon images. These temporary beacon images are
replaced with the full-quality versions as they become available, generally
about 2-3 days later.

Beacon images can always be recognized by having the character "7"
near the end of the filename, e.g. "n7euA", while the full resolution
images will have the character "4" in that location.

Also check out the write-up on
cosmic rays to see how the high
compression factors used for the beacon data affect those artifacts.

Although the initial beacon JPEG images on the browse pages are replaced by
the high resolution images as they become available, the original
FITS
versions of the beacon files are saved, and can be read using any of a large
number of
software
packages, most of which are free.